Fix crash if window is destroyed while dragging it.

ash/wm/workspace/workspace_window_resizer.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ASH_WM_WORKSPACE_WINDOW_RESIZER_H_
 #define ASH_WM_WORKSPACE_WINDOW_RESIZER_H_
 
 #include <vector>
 
 #include "ash/wm/window_resizer.h"
@@ skipping 43 matching lines @@
   bool is_resizable() const { return details_.is_resizable; }
 
   const gfx::Point& initial_location_in_parent() const {
     return details_.initial_location_in_parent;
   }
 
   // Overridden from WindowResizer:
   virtual void Drag(const gfx::Point& location, int event_flags) OVERRIDE;
   virtual void CompleteDrag(int event_flags) OVERRIDE;
   virtual void RevertDrag() OVERRIDE;
+  virtual aura::Window* GetTarget() OVERRIDE;
 
  private:
   WorkspaceWindowResizer(const Details& details,
                          const std::vector<aura::Window*>& attached_windows);
 
  private:
   FRIEND_TEST_ALL_PREFIXES(WorkspaceWindowResizerTest, PhantomStyle);
 
   // Type of snapping.
   enum SnapType {
@@ skipping 127 matching lines @@
   // been deleted.
   bool* destroyed_;
 
   DISALLOW_COPY_AND_ASSIGN(WorkspaceWindowResizer);
 };
 
 }  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_WM_WORKSPACE_WINDOW_RESIZER_H_